Charged arrays of micro and nanoscale electrochemical cells and batteries for computer and nanodevice memory and power supply

ABSTRACT

A sequence or array of electrochemical cells storing both digital and analog data. Both binary code and codes having a higher base may be stored in the memory device to increase information density. Such battery arrays could also provide power for the micro or nanodevice. Devices are microscale and nanoscale in size and utilize electrically conductive atomic force microscopy tips to record and read data stored in the device.

CROSS-REFERENCE TO PENDING APPLICATIONS

This application is based on U.S. Provisional Patent Application No.60/493,313 filed Aug. 7, 2003 and entitled “Charged Arrays of Micro andNanoscale Electrochemical Cells and Batteries For Computer andNanodevice Memory and Power Supply”.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with U.S. Government support under theDepartment of the Navy, Office of Naval Research contractN00014-01-1-0724 and the National Science Foundation contractEPS-0132534 awarded by the Department of Defense and the NationalScience Foundation. The U.S. Government has certain rights in theinvention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to microscale and nanoscale arrays ofelectrochemical cells and batteries for computer and nanodevice memoryand power supply. Specifically, the present invention relates to atwo-dimensional array of electrochemical cells or batteries that may beused to store both digital and analog information. Techniques for bothread-only and read-and-write memory storage are disclosed.

2. Prior Art

Nanotechnology is a rapidly expanding field. The desire forminiaturization of electronics, assays and memory devices stems frommany factors. Smaller devices require less material, thereby reducingproduction costs. Because the distances between points are shorter,nanoscale circuitry operates much more quickly than larger circuitboards. Information stored in very small devices may be accessed andread very quickly. Smaller devices are also less cumbersome and moreeasily transported.

The extremely high speed and small volume of microscale and nanoscalememory devices make them highly desirable. This has led to research intoa variety of methods to form extremely small memory storage devices.

Atomic force microscopy (AFM) cantilever tips have become a common toolin nanotechnology. AFM tips were originally developed in order to studysurface topography of a material at the molecular level. Changes in thesurface of as little as a few tenths of nanometers (Angstroms) may bediscerned utilizing AFM tips. When an electric current is applied to anAFM tip it may also be used for scanning tunneling microscopy (STM).This also provides for nanometer scale readings of a surface'stopography.

AFM tips have found a variety of other uses. They may be used to moveindividual atoms about a surface to create a variety of structures onthe atomic level. AFM tips have also been used to puncture holes into asurface. For example, IBM has developed a method of using AFM tips toform patterns on a pliable surface (See, for example: W. P. King, T. W.Kenny, K. E. Goodson, G. C. M. Despont, U. Durig, H. Rothuizen, G. K.Binnig, P. Vettiger, Applied Physics Letters, 78, 1300 (2001); E.Gorchowski and R. F. Hoyt, IEEE Trans. Magn. 32, 1850 (1996); D. A.Thompson and J. S. Best, IBM J. Res. Dev. 44, 311 (2000)). The surfacehas a thin layer of a material having a relatively low melting point. AnAFM tip is heated to a temperature above the surface's melting point andis applied to the surface. The tip melts a cavity into the surface. Thisdevice is used to store data in binary code. When a non-heated tip isrun across a series of holes, a hole may serve as a “1” while portionsof the material that are not punctured serve as a “0”. One disadvantageof the IBM technique is that it is difficult and time consuming toeffectively remove a single data point. Another disadvantage is that itis difficult to effectively erase stored data completely. The more datais stored and erased on a surface, the more convoluted the surfacebecomes and eventually no longer performs adequately. Anotherdisadvantage is that this technique may only store digital, binary data.

Nanoscale batteries have also been of interest as means for supplyingnanoscale devices. Thin-film rechargeable batteries with active layersof 1-10 μm have been of interest since the 1980s, and previous studieshave dealt almost exclusively with thin film work (See, for example: J.B. Bates, G. R. Gruzalski, M. J. Dudney, C. F. Lick, H.-h. Yu, and s. D.Jones, Solid State Technology, 36, No 7, 59, 1993). Thin-filmmicrobatteries have been made by a deposition technique using a metalliclithium electrode layer with a solid Li₃PO₄ electrolyte. However, thesebatteries have lateral dimensions greater than a centimeter and producedcurrent densities of only 8.3 μA/cm² at an output voltage ofapproximately 4 V. A microbattery using a Ni/Zn electrode couple with anaqueous KOH electrolyte has also been developed (See, for example: L. G.Salmon, R. A. Barksdale, B. R. Beachem, R. M. LaFollette, J. N. Harb, J.d. Holladay, and P. H. Humble, “Development of RechargeableMicrobatteries for Autonomous MEMS Applications,” in Solid-State Sensorand Actuator Workshop (Transducer Research Foundation, Inc. Hilton Head,S.C., 1998) pp 338-341). Once again, fabrication involves a depositionprocess for the two electrodes, with a polymer layer that is laterremoved to form the electrolyte cavity. These planar microbatteries were200 μm×200 μm and had capacities of 200-200 mC/cm² at current densitiesof 10-20 mA/cm² with an operating voltage of 1.5 V. A carbon-basedrechargeable lithium microbattery has been contemplated, but theprogress in fabricating the electrode microstructure has been slow. Thistechnology is based on photoresist technology commonly used in thesemiconductor industry and electrodes are to be made from arrays ofmicroelectrodes having diameters as small as 5 μm (See, for example:Kinoshita, K., Song, X., Kim, J., Inaba, M., Kim, J., Journal of PowerSources 82, 170 1999). The majority of the most recent papers onmicrobatteries follow these trends by describing systems where very thinfilms of electrolyte material were used to construct the battery, or bydiscussing the potential for these films to be used in batteries. Theactual size of the batteries based on the electrode structure is muchgreater than the nanometer scale. (Levasseur, A., Vinatier, P., Gonbeau,D., Bull. Mater. Sci. 22 (3), 607 (1999); Han, K. S., Tsurimoto, S.,Yoshimura, M., Solid State Ionics 121 (1-4), 229 (1999); Park, Y., Kim,J. G., Kim, M. K., Chung, H. T., Um, W. S., Kim, M. H., Kim, H. G., J.Power Sources 76 (1), 41 (1998); N. C. Li, C. J. Patrissi, G. G. Che,and C. R. Martin, J. Electrochem. Soc., 147, 2044 (2000); N. C. Li, C.R. Martin, and B. Scrosati, Electrochem. And Solid State Lett., 3, 316(2000))

Additional attempts have been made to fabricate micro and nanobatterycomponents and systems taking advantage of nanoscale technology andassembly. Nanoscale electrode systems have been made using a templatesynthesis method. Systems composed of LiMn₂O₄, SnO₂, TiS₂, sol-gel V₂O₅materials, and carbon tubes have been used to make nanoscale electrodematerials that typically show higher capacities, lower resistance, andlower susceptibility to slow electron-transfer kinetics than standardelectrode configurations (V. M. Cepad, J. C. Hulteen, G. Che, K. B.Jirage, B. B. Lakshmi, E. R. Fisher, and C. R. Martin, Chem. Mater. 9,1065 (1997); C. J. Patrissi and C. R. Martin, 146, 3176 (1999); G. G.Che, B. B. Lakshmi, E. R. Fisher, and C. R. Martin, Nature 393, 346(1998); S. V. Batty, T. Richardson, F. B. Dias, J. P. Voss, P. V.Wright, and G. Ungar, Thin Solid Films, 284-285, 530 (1996); Y. Zheng,F. B. Dias, P. V. Wright, G. Ungar, D. Bhatt, S. V. Batty, and T.Richardson, Electochim. Acta, 43, 1633 (1998)). Langmuir-Blodgett filmshave been made that have ion-conducting layers that have the potentialto be used as electrolytes in nanobattery systems. Self-assemblymechanisms may also be used to construct a high energy densityrechargeable lithium ion batteries by using a layer-by-layerself-assembly of poly(diallyldimethyl-ammonium chloride), graphite oxidenanoplatelets and polyethylene oxide on indium tin oxide with a lithiumwire as a counter electrode. Systems with 10 self-assembled layers havehigh specific capacities ranging from 1100 to 1200 mAH/g. (J. H.Fendler, J. Dispersion. Sci. Tech., 20, 13 (1999); S. Vorrey and D.Teeters, Electrochimica Acta, 48, 2137 (2003); A. L. Layson, ShaileshGadad, Dale Teeters, Electrochimica Acta, 48, 2207 (2003)).

Assignee is the owner of U.S. Pat. No. 6,586,133 for “Nano-BatterySystems” which is incorporated herein by reference, and which disclosesa process of providing a membrane with a plurality of pores, filling themembrane pores with an electrolyte, and capping the filled pores withelectrodes.

The use of AFM tips for fabrication and data storage has evolvedseparately from the techniques being developed for making nanoscalebatteries. Nothing in the prior art has contemplated the use of arraysof miniaturized batteries to store data at a very small scale.

It is therefore desirable to develop a nanoscale storage device that maybe erased and rewritten several times without deteriorating.

It is also desirable to develop a nanoscale memory device capable ofstoring analog information.

It is also desirable to provide a nanoscale memory device that uses andelectronic charge or current to store both erasable and permanentinformation.

SUMMARY OF THE INVENTION

The present invention provides a memory storage device that is extremelysmall, efficient, fast, reliable and durable. It is comprised of severalmicroscale or nanoscale electrochemical cells or batteries arrayed insequence. Data is stored by either applying a charge to each cell or bydesigning various cells to produce a specific voltage when current isapplied. An AFM tip or other type of current conducting probe ofappropriate size is applied to the various cells or batteries insequence to detect either the presence or lack of a charge or the levelof conductance of a cell or battery.

Those skilled in the art will appreciate that various anode/cathodecombinations provide electrochemical cells having a specific voltage.For example, electrochemical cells may be formed having either zinc orcadmium functioning as an anode. A silver cathode may be applied to theelectrolyte of each of these cells. When a current is run through thecell being measured, cells having a cadmium anode will produce adifferent voltage than cells having a zinc anode. These two differentvalues of voltage may serve as 0' s and 1' s.

Those skilled in the art will appreciate that there are a wide varietyof materials with different electrochemical potentials suitable asanodes and cathodes. Each one provides a different electrochemicalpotential with a particular complementary electrode. Those skilled inthe art will appreciate that this means that the present invention iscapable of storing data in more than just binary code. The presentinvention allows information to be stored in codes having a base ofthree, four, five or even higher. This greatly increases the storagecapacity of the memory device.

Data may also be stored using a more conventional binary system.Electrochemical cells may have a charge applied to them. A sequence ofcells will comprise several cells, some of which are charged, and someof which are not. An uncharged cell may serve as a “0” and a chargedcell may serve as a “1” in a common binary coding method. An AFM tip orother type of current conducting probe is used to apply a charge tovarious cells as the information is written upon the storage device. Thesame or another AFM tip or other type of probe may be later applied tothe various cells to detect the presence or absence of a charge. In thisfashion, the storage device may be read. This design provides for verysimple and efficient write over or erasing of the memory device.

The electrochemical cells or batteries used in the present invention areformed in very small pores in a substrate film. Pores may be formedusing a laser ablation, photolithographic techniques or other methodsknown in the art. The pores are then filled with an electrolytematerial. Electrodes are then placed on either end of the pores. Some ofthe preferred methods of forming these nanoelectrochemical cells aredescribed in Assignee's U.S. Pat. No. 6,586,133 to Teeters et al., whichis hereby incorporated by reference. Instead of pores the individualmicro and nanocells could be manufactured by standard integrated circuittechniques. For example the arrays of cathodes and anodes could bedeposited by chemical vapor deposition techniques or physical vapordeposition techniques in to patterns created by photo resist technology.Likewise a solid electrolyte could be deposited by the same chemicalvapor and physical vapor deposition techniques. The connections betweenthe individual cells could also be made by deposition onto patternscreated by photo resist techniques. Micro and nanolithographictechniques could also be used to create the pores for the electrolyteand to connect the individual cells or batteries. For example e-beamlithography or focused ion beam lithography could be used to create thepores for the batteries. Nanolithography techniques could be used toconnect the individual cells or batteries. For instance focused ion beamlithography can be used to deposit the metallic connections between someor all of the individual batteries.

Those skilled in the art will appreciate that there are alternativemethods of forming the cells. The cells could also be assembled bychemical self-assembly techniques where surfactant molecules or blockcopolymers would assemble on a flat cathode or anode substrate. In thistechnique the surfactant molecules and the block copolymers are composedof polar and nonpolar regions. When dissolved in a nonpolar solvent, thepolar part of the molecule or copolymer will associate inside thenonpolar part of the surfactant molecule or copolymer forming a core ofthe polar material. When this solution is cast on a solid substratemaking a thin film, evaporation of the solvent results inevaporation-induced self-assembly where the core polar material issurrounded by nonpolar material. This forms very ordered arrays ofchannels of the polar material. The polar materials in these surfactantsand block copolymers would be of a chemical composition suitable forelectrolyte use. Thus the micro and nanopores for the electrolyte wouldbe made (See, for example: T. Thurn-Albrecht, R. Steiner, J. DeBouchey,C. M. Stafford, E. Huang, M. Bal, M. Tuominen, C. J. Hawker and T.Russell, Adv. Mater., 12, 787 (2000)). The appropriate electrode couldbe placed on the pores or channels of electrolyte by placing thesubstrate in a solution containing suspended nanoparticles of thecorrect size to cover the pores or channels. The anode particles couldthen be made to adsorb from solution onto the pores, covering them andmaking the electrode. Alternatively, integrated circuit lithographictechniques, e-beam lithography or focused ion beam lithography could beused to make the electrode on top of the pores. Those skilled in the artof chemical self-assembly, integrated circuit lithographic techniques,e-beam lithography, focused ion beam lithography or other suchtechniques will appreciate that there are alternative methods of formingthe cells.

The cells or batteries are preferably formed in a large array. SeveralAFM tips may be used simultaneously to read or write data on the device.Because the cells may also serve as electrical power supplies for microand nanoscale devices, an array may include more than just cells orbatteries utilized for data storage. A portion of an array may beutilized as a power source for a microscale or nanoscale device. Thus,the present invention may serve as both data storage and a power supplyfor extremely small scale machinery and devices.

Another significant advantage of the present invention is its ability torecord analog information. While known methods of data storage utilizingAFM tips may only be used for digital storage, the present invention hasfar broader applications. When accessed by the AFM tip or other probe,the voltage of cells having various anode/cathode combinations changeswith time through the natural discharge process of the cell. An AFM tipmay be programmed to first contact the cell having a various anode orcathode prior to measurements. It may be programmed to measure voltageafter a certain period of time has lapsed. This allows the value of thevoltage measured to vary across a continuous spectrum of time within arange of voltages. Similarly, a charged battery cell shows a decreasedcharge over time. The charge decreases over time such that an AFM tipmay be programmed to record the charge level after a specific timeperiod has lapsed. This allows charged readings to be taken anywherealong a continuous range of charges. Both of these methods provide forthe reading of a value somewhere within a continuous spectrum. Thisallows storage of analog data that is not possible with storage devicesthat only provide for reading and writing of digital data. Those skilledin the art will appreciate that this also provides a significantadvantage over the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a nanobattery;

FIG. 2 schematically shows how an AFM tip is used to charge or testnanobatteries or microbatteries;

FIG. 3A shows how an AFM tip is used to measure the voltage of ananocell or microcell;

FIG. 3B shows how an AFM tip is used to measure the voltage of ananocell or microcell;

FIG. 4 shows a schematic view of an array of nanocells or nanobatteries;

FIG. 5 shows an array of AFM tips for testing, reading or writing ontoan array of nanobatteries or nanocells;

FIG. 6 is a graph of potential versus time for two nanobatteries;

FIG. 7 is a three-dimensional graph showing how voltage decay rates ofan individual electrochemical cell may be varied by changing thedischarge rate of that cell when measuring its potential; and

FIG. 8 is a depiction of an electron microscope view with an array ofpores, some of which are filled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments discussed herein are merely illustrative of specificmanners in which to make and use the invention and are not to beinterpreted as limiting the scope of the instant invention.

While the invention has been described with a certain degree ofparticularity, it is to be noted that many modifications may be made inthe details of the invention's construction and the arrangement of itscomponents without departing from the spirit and scope of thisdisclosure. It is understood that the invention is not limited to theembodiments set forth herein for purposes of exemplification.

The present invention comprises a device capable of storing informationfor computer applications and in microscale and nanoscale devices. Bothdigital and analog information may be stored. In addition, systemsgreater than base 2 may be designed. By using trinary or greatersystems, the amount of data stored can be greatly increased. Forexample, three data points in a binary system allow for eight possiblepermutations. In a trinary system three data points allow for 27possible permutations, more than a three-fold increase. Using a basefour system allows for 64 permutations using only three data points.Those skilled in the art will appreciate that the ability to expandbeyond the binary information storage system may increase the storagecapacity of a memory device by an order of magnitude.

In the present invention, information is generally stored by forming asequence of microscale or nanoscale electrochemical cells. A typicalcell is shown in FIG. 1. Electrochemical cell 10 is comprised of anelectrode 12, an electrolyte 14 and a second electrode 16. The cell isincorporated into a substrate (not shown) using the methods described inU.S. Pat. No. 6,586,133, photolithography or other methods known in theart. AFM tip 17 or other type of current conducting probe of theappropriate size is applied to electrode 16. It is comprised of acantilever 18 and a tip 19. Those skilled in the art will recognize thisas a relatively standard AFM tip well known in the art. In the presentinvention, AFM tip 17 is electrically conductive. It is also connectedto instrumentation 20 by circuit 22. Instrumentation 20 is alsoconnected to electrode 12 by circuit 24. When electrically conductiveAFM tip 17 is applied to electrode 16, instrumentation 20 may be used todetect a charge and/or the potential of the cell 10.

AFM tip 17 may also be used to apply a charge to cell 10 that isprovided by instrumentation 20. Once a charge is applied, AFM tip 17 ora similar tip may be used to read the presence or absence of a charge.Similarly, an AFM tip may be used to remove a charge in cell 10.

Electrodes 12 and 16 may be comprised of any material suitable as anelectrode. The following are compounds and materials that could be usedfor electrode materials, especially for lithium ion based batterysystems. These materials or the corresponding alkali or alkaline metalion materials could be used for battery systems based on the alkali oralkaline metals. The general class of these compounds is given aboveeach group.

Inorganic Oxide Compounds

MoO₃, Cr₃O₈, V₂O₅, V₆O₁₃, LiV₃O₈, MnO₂, LiCoO₂, LiNiO₂, LiMn₂O₄, LiVO₂,LiCrO₂, WO₃, TiO₂.

Inorganic Chalcogenides

TiS₂, MoS₂, NiPS₃, TiSe₃, TiTe₂, MoS₂, MoSe₂, InSe.

Carbon and Fluorocarbon Compounds

Coke, Graphite, CF_(n), (C₂F)_(n), C₇CoCl₂.

Polymeric Materials

poly(acetylene), poly(pyrrole), poly(vinylferrocene), poly(aniline),poly(p-phenylene), poly(phenylene sulfide).

Those skilled in the art will appreciate that there is a wide variety ofsuitable materials.

Electrolyte 14 may similarly be comprised of any number of materials, solong as it is suitably ionically conductive. Electrolyte 14 is typicallya solution having either an aqueous or solid solvent and a solutecapable of carrying a charge. Those skilled in the art will appreciatethat there is a wide variety of solvent compounds as well as inorganicions that will serve as suitable charge carrying solutes in thesolvents. The following is a list of example materials that could beused for electrolyte materials. These are both liquid and solids:

-   -   Aqueous (water) solutions containing appropriate ionic salts    -   Poly(ethylene oxide) containing appropriate ionic salts    -   Poly(propylene oxide) containing appropriate ionic salts    -   Polyethylene glycols containing appropriate ionic salts    -   Polypropylene glycols containing appropriate ionic salts    -   Propylene carbonate containing appropriate ionic salt    -   Ethylene carbonate containing appropriate ionic salt    -   Comb-branched systems comprised of low molecular weight        polyether chains grafted to polymer backbone. These must contain        an appropriate ionic salt.

Gel electrolyte materials—These consist of polymer hosts such aspolystyrene, poly(vinyl chloride), poly(vinyl alcohol),polyacrylonitrile, poly(vinylidene fluoride), and poly(ethylene oxide),which have had materials like propylene carbonate, ethylene carbonate,dioctyl sebacate, or diethyl phthalate added as plasticizers. Thesematerials must contain an appropriate ionic salt.

Lithium Phosphorous Oxynitride

One type of battery suitable for use in the present invention is alithium polymer battery. Lithium polymer batteries (LPBs) can be broadlydefined as an all-solid-state system that, in their most common form,uses two lithium reversible electrodes with a lithium ion conductingpolymer membrane as the electrolyte. The LPB cathode is usually based ona reversible intercalation compound (for instance TiS₂, V₆O₁₃, LiV₃O₈,TiO₂, LiMn₂O₄, etc.) blended with small portions of the polymerelectrolyte and carbon to form a composite material. The carbon blackincreases the electron conduction of the composite cathode while thepolymer electrolyte serves as binder for the cathode. When the cathodematerial is used as a nanoscale electrode, electrical conduction is nota problem because the particle is so small and/or thin that lowelectrical conduction is not a problem. Thus when making the nanobatteryusing nanoparticles or films of intercalation compounds that are lessthan 5.5 μm in thickness, we can use the pure intercalation compoundwithout the need for a composite system with a high electron conductingmaterial. The anode can be lithium metal or a lithium ion sourceelectrode.

Other lithium batteries exist that do not use polymer electrolytes. Onesuch battery uses lithium phosphorous oxynitride. This type ofelectrolyte can be deposited by a sputter coating process. The fact thatthis electrolyte can be sputter coated on the same anodes and cathodesas listed above for LPBs makes it an interesting electrolyte fornanobattery manufacturing.

Nanobatteries have been made from various cathode and anode materialssuch as graphite, LiMn₂O₄, LiCoO₂, V₂O₅, and SnO₂. These nanobatteriesmay be made using nanoporous membranes with well defined pores orchannels. Those skilled in the art will appreciate that these are only afew of the many materials that may be used to form suitablenanobatteries for use in the present invention.

FIG. 2 shows a memory device 30 composed of a series of electrochemicalcells in a substrate. Substrate 32 has a series of pores 35 into whichelectrolyte 37 has been placed. Electrode 34 coats the entire bottomportion of substrate 32, serving as an electrode for all theelectrochemical cells 31. Electrode 34 is connected to instrumentation36 by circuit 38. Instrumentation 36 is capable of measuring theelectric potential of the individual cells 31, detecting the presence ofa charge in a cell 31 and applying a charge to cells 31. Eachelectrochemical cell has a top electrode 39. These may be comprised ofnanoparticles placed on top of wells 35 after electrolyte 37 has beenplaced in the pores. Electrodes 39 may also be formed usingphotolythographic or other techniques known in the art. Electrodes 39may all be comprised of the same conductive material. Alternatively,electrodes 39 may be comprised of different materials. If electrodes 39are composed of different materials they will form electrochemical cellshaving different open circuit potentials.

Instrumentation 36 is also attached to AFM tip 46 or other type ofcurrent conducting probe by circuit 40. AFM tip 46 is electricallyconductive and comprises a cantilever 42 and a tip 44. As the tip 46moves across substrate 32 it will come into contact with the electrodes39 of cells 31. Because electrodes 39 protrude upwardly from substrate32, tip 46 will likewise move upwardly when it comes in contact withthem. This causes tip 46 to move up and down as shown by arrow 54 as itis moved across substrate 32. This motion is detected by using a lasergenerating device 48 that emits a laser 52 which reflects off tip 46 atpoint 51. When tip 46 moves up or down, the angle of reflection of laser52 changes. Changes in reflection of laser 52 may be detected by sensor50. When sensor 50 detects that tip 46 has moved in an upward direction,the operator will know that it has come into contact with an electrode39. When this determination is made, instrumentation may be used todetect a charge, measure potential or apply a charge. This preventsaccidental readings of zero charge or zero potential on substrate 32.Alternatively the entire surface of memory device 32 could have beencharacterized by the AFM previously. The AFM tip or other type ofcurrent conducting probe of the approximate size could then be movedexactly to the location of one of the electrodes 39 to detect a charge,measure potential or apply a charge.

The tip 46 may be used to erase data stored on storage device 30 bycontacting each electrode 39 and removing any charge present. Once allcharges are removed, storage device 30 is erased and contains noinformation recorded by the presence or absence of a charge. However, ifelectrodes 39 are comprised of differing materials, permanent,non-erasable data is still stored and detectable by measuring thediffering potentials of the various electrodes.

Tip 46 may be used to apply a charge provided by instrumentation 36 tovarious electrodes. This will result in a sequence of electrodes thatare either charged or uncharged. This may be used to store binary,digital information. Tip 46, or another AFM tip or other type of currentconducting probe may later move across the same electrodes, detectingthe presence or absence of a charge thereby reading a binary sequence inwhich information is stored.

One of the benefits of the present invention is that, because electrodes39 may be composed of different materials, binary information may berecorded and erased by charging and discharging cells 31. This iscombined with a permanent, non-erasable set of information stored by thedifferences in cell potential of the various electrodes. By using laser52 to detect when tip 46 is in contact with and out of contact withcells 31, errors in reading the stored data is prevented.

FIG. 3A shows an alternative embodiment of the present invention. Inthis embodiment, storage device 60 has electrolyte material 70 withinpores 71 of substrate 68. Underneath each of pores 71 is an electrode,either 78 or 80. For instance, electrodes 78 could be comprised of zinc,while electrodes 80 are comprised of cadmium. Electrodes 78 and 80 areconnected to instrumentation 72 by circuit 76. Instrumentation 72 isalso connected to AFM tip 66 by circuit 74. AFM tip 66 is comprised ofcantilever 62 and tip 64. In this particular embodiment, tip 66 iscoated with silver so that it is electrically conductive. In thisembodiment, tip 64 serves as a second electrode such that pores 71 mayserve as electrochemical cells. As tip 66 is moved across substrate 68,it comes in contact with the electrolyte materials 70 found in pore 71.In FIG. 3A, tip 64 has come in contact with electrolyte material 70 thatis above the cadmium electrode 80. Instrumentation 72 measures thepotential in volts across the electrolyte material between tip 64 andelectrode 80. As shown in the figure, electrochemical cell having asilver cathode and cadmium anode has a potential of approximately 1.4volts. Alternatively, the entire surface of memory device 60 could havebeen characterized by the AFM previously. The AFM tip or other type ofcurrent conducting probe could then be moved exactly to the location oneof the electrodes 39 to measure potential.

FIG. 3B shows the same embodiment as shown in FIG. 3A wherein tip 66 hasmoved across substrate 68 such that it is in contact with electrolytematerial above the zinc electrode 78. As with FIG. 3A, theinstrumentation 72 measures the potential across the electrochemicalcell comprised of a silver cathode and zinc anode. Here, the potentialmeasured is approximately 1.85 volts. By forming the series of partialelectrochemical cells having differing anodes, in this case zinc andcadmium, information may be permanently stored in binary code on memorydevice 60. The sequence, and therefore the information stored, may onlybe changed by replacing the anodes.

In the embodiment shown in FIGS. 3A and 3B, only zinc and cadmium areused as anodes. However, those skilled in the art will appreciate thatthere are many materials having different electrochemical potentialsthat are suitable for forming anodes or cathodes. Those skilled in theart will appreciate that using materials in addition to zinc and cadmiumwill result in the ability to store information using more than a binarysystem such as a trinary system or even systems of base 4, 5 or more.

This embodiment lacks protruding upper electrodes on the top side ofsubstrate 68 covering electrolyte material 70 as compared to theembodiment in FIG. 2. This is intended to show that permanentinformation storage by alternative electrode material does not require asecond, permanent electrode. The tip 64 itself may serve as the secondelectrode in the electrochemical cell. In this embodiment, a laser isnot used to determine when tip 64 is in contact with the appropriatepart of the substrate, the electrolyte material. However, thisembodiment does not require such a safeguard, because all theelectrochemical cells will exhibit at least some potential. When tip 64is in contact with the substrate, there will be zero potential. However,as shown in FIG. 2, information storage by means of altering anodecomposition may be used in conjunction with permanent second anodes.

FIG. 4 shows a preferred embodiment of storage device 90. The storagedevice 90 is comprised of a substrate 94 having a two-dimensional arrayof electrochemical cells 92. An array such as this may be utilized forall of the embodiments disclosed herein. In the array shown in FIG. 4, arow of electrodes 93 may be set aside from the rest of the array. Whilethe majority of the array is used for data storage detected by eithermeasuring charge or potential, the row of electrodes 93 is comprisedentirely of charged electrochemical cells. Row 93 may be utilized as apower supply for a device that reads the information stored in theremainder of the array. This greatly eases manufacture of microscale andnanoscale devices and increases their utility, as the informationstorage component and the power supply have been combined into onedevice. Those skilled in the art will appreciate that this will greatlysimplify manufacture of extremely small scale devices, such asmicroelectrical mechanical systems (MEMS) and nanoelectromechanicalsystems (NEMS). This increases the potential to enhance the capabilityof micro and nano devices.

FIG. 5 shows an array of AFM tips 100 or these could represent arrays ofother types of current conducting probes. It is comprised of multipleAFM tips or other type of current conducting probes 104 that are alignedso that they may be moved across substrate 102 to measure potentialand/or charge of electrochemical cells in substrate 102 representing thearray of micro or nanocells or batteries shown in FIG. 4. Circuits 108and 106 form a grid pattern across the AFM tip array 100 and are used toconnect the individual AFM tips to instrumentation capable of measuringpotential, measuring charge and applying charge to variouselectrochemical cells within the substrate 102. Those skilled in the artwill appreciate combining the electrochemical cell array 90 with AFM tiparray 100 will greatly increase the speed with which data may be storedon a memory device or read off of a memory device (See, for example: W.P. King, T. W. Kenny, K. E. Goodson, G. C. M. Despont, U. Durig, H.Rothuizen, G. K. Binnig, P. Vettiger, Applied Physics Letters, 78, 1300(2001); E. Gorchowski and R. F. Hoyt, IEEE Trans. Magn. 32, 1850 (1996);D. A. Thompson and J. S. Best, IBM J. Res. Dev. 44, 311 (2000)).

One general method of forming an array of cells is to use self-assemblytechniques where surfactant molecules or block copolymers would assembleon a flat cathode or anode substrate (See, for example: T.Thurn-Albrecht, R. Steiner, J. DeBouchey, C. M. Stafford, E. Huang, M.Bal, M. Tuominen, C. J. Hawker and T. Russell, Adv. Mater., 12, 787(2000)). The surfactant molecules and the block copolymers are composedof polar and nonpolar regions. In one form of this technique, thesurfactants or copolymer are dissolved in a nonpolar solvent. The polarpart of the surfactant or block copolymer will associate inside thenonpolar part of the surfactant molecule or copolymer forming a core ofthe polar material. When the solution of the block copolymer orsurfactant is cast on a solid substrate making a thin film, evaporationof the solvent results in evaporation-induced self-assembly where thecore polar material is surrounded by nonpolar material forming veryordered arrays of channels of the polar material. The polar materials inthese surfactants and block copolymers would be of a chemicalcomposition suitable for electrolyte use. Thus, the nanopores for theelectrolyte would be made. A second method would be to use spin-coatedfilms and to apply an electrical potential during an annealing process.The applied field causes the self-assembly of the block copolymer orsurfactant to orient the polar material into ordered arrays ofelectrolyte channels. Capping the pores with an anode or cathode isaccomplished by placing the substrate in a solution containing suspendedcathode or anode nanoparticles of the correct size to cover the pores orchannels. The appropriate electrode nanoparticles, which can now bepurchased from commercial sources, could then be made to adsorb fromsolution onto the pores by applying a potential. Another method would bea form of dip coating where the film is submerged into a liquid havingthe nanoparticles suspended. As the film is removed from the liquid, themovement of the liquid/solid contact line would force the particles intothe pore openings.

This technique has advantages in terms of the relative ease and costeffectiveness of self-assembly methods. The technique also makes filmshaving a high pore density where the pore size can be as small as from1-10 nm.

Another method is to use aluminum oxide membranes. Alumina membraneshaving hexagonally ordered pores may serve as the template for thenanobattery arrays. The process for making these membranes consists ofapplying an electrical potential to an aluminum sheet while in an acidsolution. This results in the formation of a porous aluminum oxide filmthat does not have the regular arrangement of pores necessary forordered arrays. This oxide layer is removed by an acid wash; however,ordered pits in the original aluminum sheet remain. These pits serve asthe template for the a porous oxide layer formed from a secondapplication of current in the acid solution. Because of the ordered pitsin the aluminum film, the second oxide layer formed has very orderedpores in a hexagonal configuration. Changing the applied voltage and thetype of acid used controls the pore diameter. This technique makes veryordered arrays of pores in alumina membranes with pores 120 nm indiameter and smaller (See, for example: H. Masuda, K. Nishio and N.Baba, Thin Solids Films, 223, 1, (1993); H. Masuda and K. Fukuda,Science, 268, 1466 (1995); A.-P. Li, F. Muller, A. Birner, K. Neilsch,and U Gosele, Adv. Mater. 11, 483 (1999); I. Mikulska, S. Juodkazis, R.Tomasiunas, and J. G. Dumas, Adv. Mater. 13, 1574 (2001)). Thesemembranes may be used in the manufacture of ordered arrays ofnanobatteries. Microbatteries with nanosized cathodes or anodes may beformed by filling the pores in the alumina membranes with sol gelmaterials that are cathode materials such as V₂O₅ or cathode materialssuch as SnO₂. (See, for example: H. Liu, Y. P. Wu, E. Rahm, R. Holze, H.Q. Wu, Journal of Solid State Electrochemistry 8 (7), 450 (2004); C.-T.Hsieh, J.-M. Chen, H.-W. Huang, International Journal of Nanoscience, 2(4&5) 299 (2003)). This can be accomplished by using a nanocoatingtechnique (See, for example: C. Dewan and D. Teeters, Journal of PowerSources 119-121C, 460 (2003)). Excess from the surface can be removedleaving a filled pore. This is shown in FIG. 8.

Where, for comparison, some 200 nm pores have been filled, and othersleft unfilled. In the actual process all pores would be filled makingarrays of nanobatteries.

Another method of fabrication is the use of microlithographic techniquestaking advantage of e-beam lithography, resist technology and sputtercoating to make nanobattery arrays. In this method, a cathode or ananode material will be sputter coated on a current-collecting metalsubstrate. A resist layer will be deposited by spin coating on thedeposited cathode. Patterns consisting of ordered arrays of holes willbe made by electron exposure to the regions that are to be the holes.Positive resist techniques will be used where the electron-exposed areaswill be more soluble in a developer. Exposing the substrate to thedeveloper will remove the e-beam exposed resist, leaving the desiredordered array in the remaining resist. Next, sputter coating is used todeposit an electrolyte and anode or cathode layer, which ever is neededto complement the first layer deposited, over the remaining resist andon the exposed anode or cathode layer in the areas where no resistremains. Lithium phosphorous oxynitride is used as the electrolyte layersince it is a good solid electrolyte that lends itself well to sputtercoating. This layer is be deposited first, followed by a layer of anodematerial such as SnO₂ that is also sputter coated onto the lithiumphosphorous oxynitride layer. At this point, the remaining resist isremoved by a solvent and the lithium phosphorous oxynitride and anodelayers on the resist are removed in what is called the “liftoff”process. This leaves the ordered arrays of lithium phosphorousoxynitride and anode resting on a cathode substrate. The description ofthis process has been somewhat simplified. For instance, undercutting ofthe resist holes may be necessary to get well-formed stacks of lithiumphosphorous oxynitride and anode for each nanobattery. Otherconfigurations of resist may be used to make the appropriate nanobatterystructures. Nanobatteries with diameters as small as 250 nm with aseparation distance of 250 nm are easily made.

The common use of microlithographic techniques by the integrated circuitindustry is a great advantage for the development of nanobattery arraysusing this technique. The general techniques are well known and by usingthese techniques, one will be assured of making ordered arrays. Anotheradvantage of this proposed process is that the thin film batterysystems, made by the sputter coating technique described above, performwell and are mechanically and chemically stable.

The embodiments described above and the methods of reading informationoff of the storage devices are described in terms of recording digitalinformation. One of the advantageous of using a system that measurespotential and/or charge of individual electrochemical cells is that itmay also be utilized to store and read analog data. This is because bothcharge and potential of the cells described above will decrease overtime. The change in potential or charge over time follows a measurablerate of decay. FIG. 6 shows two examples of experimental data collectedof how an electrochemical micro cell's potential decreases over time.The slopes of the lines 120 and 122 shown in FIG. 6 are continuousacross a range of potential. In order to read analog information, theAFM tip used to read an electrochemical cell is applied to that cell.Instrumentation may be easily programmed to wait a set time period afterthe tip contacts the electrochemical cell before measuring either chargeor potential. This allows the instrumentation to record a value anywherewithin the range of maximum and minimum potential of the cell.

Those skilled in the art will appreciate that measuring analog data of acharged cell will drain the charge of the cell. Before such data may beaccurately reread, the cell must be recharged. However, the potential ofan uncharged electrochemical cell exhibits the same decline over timeand naturally returns to its maximum level eventually. This allows foreasily rereading electrochemical cells. In addition, one electrochemicalcell is capable of storing several analog data points. Theinstrumentation need only be programmed to measure the potential atdifferent time points. In this fashion, several analog data points maybe measured from a single electrochemical cell.

Additional storage capacity can be obtained by controlling the rate atwhich the batteries are allowed to be discharged. For instance, if thebattery was discharged at its theoretical capacity it would have onedischarge rate or rate of voltage decay. If it were discharged at twiceits theoretical discharge rate it would have a different voltage decayrate. This is shown in FIG. 7. Three-dimensional graph 130 shows aseries of lines 132 that plot the voltage decay of an electrochemicalcell over time at varying discharge rates. As the discharge rate isincreased, so is the rate of voltage decay. The instrumentation needonly be programmed to measure the potential at different time points anddischarge rates. In this fashion 3-dimensional storage of data can beaccomplished resulting in an even higher density of data points beingstored.

Whereas, the present invention has been described in relation to thedrawings attached hereto, it should be understood that other and furthermodifications, apart from those shown or suggested herein, may be madewithin the spirit and scope of this invention.

1. An electrochemical device, comprising: a substrate having a topsurface and a bottom surface; an array of electrochemical cells, each ofsaid electrochemical cells comprising a first electrode, a secondelectrode and an electrolyte, wherein the first electrode is on the topsurface of the substrate, wherein said electrochemical cells havediffering open circuit potentials; at least one electrically conductiveprobe capable of coming into electrically conductive contact with thefirst electrode; and electronic instrumentation capable of applying acharge, reading a charge, or discharging the electrochemical cells atdifferent rates and measuring potential of the electrochemical cells asa function of time, wherein the instrumentation is in electricallyconductive contact with the at least one probe.
 2. The device of claim 1wherein the electrochemical cell comprises a pore that extends from thetop surface of the substrate to the bottom surface of the substrate,wherein the electrolyte is in the pore and the second electrode is onthe bottom surface of the substrate.
 3. The device of claim 1 whereinthe probe comprises an atomic force microscopy tip.
 4. The device ofclaim 1 wherein the probe comprises a plurality of probes.
 5. The deviceof claim 3 further comprising a means of determining when the tip is inelectrically conductive contact with the first electrode.
 6. The deviceaccording to claim 5 wherein the means of measuring when the tip is inelectrically conductive contact with the first electrode comprises alaser beam.
 7. The device of claim 1 wherein the second electrodes ofthe array of electrochemical cells are in electrically conductivecontact with each other.
 8. The device of claim 1 wherein the secondelectrodes are comprised of multiple materials.
 9. The device of claim 1wherein the first electrodes of the array of electrochemical cellscomprise differing materials allowing permanent non-erasable data to bestored and detected by measuring the differing potentials of the firstelectrodes and/or binary information to be recorded and erased bycharging and discharging the electrochemical cells.
 10. The device ofclaim 9 wherein at least one row of said array of electrochemical cellscomprises charged electrochemical cells to be utilized as a power supplyfor said device, and wherein the remainder of said array ofelectrochemical cells comprises information storage electrochemicalcells to be utilized for data storage detected by either measuringcharge or potential for said device.
 11. An electrochemical device,comprising: a substrate having a top surface and a bottom surface; anarray of electrochemical cells, each of the electrochemical cellscomprising a first electrode, and an electrolyte, wherein the firstelectrode is on the top surface of the substrate and in electricallyconductive contact with the electrolyte, wherein the electrochemicalcells have differing open circuit potentials: at least one secondelectrode on the bottom surface of the substrate and in electricallyconductive contact with the electrolyte, an array of electricallyconductive probes capable of coming into electrically conductive contactwith the first electrode; and electronic instrumentation capable ofapplying a charge, reading a charge, or discharging the electrochemicalcells at different rates and measuring potential of the electrochemicalcells as a function of time, wherein the instrumentation is inelectrically conductive contact with the at least one probe.
 12. Thedevice of claim 11 wherein the electrochemical cell comprises a porethat extends from the top surface of the substrate to the bottom surfaceof the substrate, wherein the electrolyte is in the pore and the secondelectrode is on the entire bottom surface of the substrate.
 13. Thedevice of claim 11 wherein the array of electrically conductive probescomprises an array of atomic force microscopy tips.
 14. The device ofclaim 13 further comprising a means of determining when each of the tipsare in electrically conductive contact with the respective firstelectrode.
 15. The device according to claim 14 wherein the means ofmeasuring when the tips are in electrically conductive contact with thefirst electrode comprises a laser beam.
 16. The device of claim 11wherein the at least one second electrode comprises a plurality ofsecond electrodes.
 17. The device of claim 16 wherein the secondelectrodes are in electrically conductive contact with each other. 18.The device of claim 16 wherein the second electrodes are comprised ofmultiple materials.
 19. The device of claim 11 wherein the firstelectrodes of the array of electrochemical cells comprise differingmaterials allowing permanent, non-erasable data to be stored anddetected by measuring the differing potentials of the first electrodesand/or binary information to be recorded and erased by charging anddischarging the electrochemical cells.
 20. The device of claim 19wherein at least one row of said array of electrochemical cellscomprises charged electrochemical cells to be utilized as a power supplyfor said device, and wherein the remainder of said array ofelectrochemical cells comprises information storage electrochemicalcells to be utilized for data storage detected by either measuringcharge or potential for said device.
 21. An electrochemical device,comprising: a substrate having a plurality of pores extending from a topsurface of said substrate to a bottom surface of said substrate, whereineach of said pores is filled with an electrolyte thereby forming atwo-dimensional array of electrochemical cells; at least one firstelectrode on at least a portion of said top surface of said substrateand in electrically conductive contact with said electrolyte of saidarray of electrochemical cells; at least one second electrode on atleast a portion of said bottom surface of said substrate and inelectrically conductive contact with said electrolyte of said array ofelectrochemical cells; an array of electrically conductive probescapable of coming into electrically conductive contact with said firstelectrode to respectively apply a charge, read a charge, or dischargeeach of said electrochemical cells at differing rates and/or measurerespective potentials of each of said electrochemical cells; wherein atleast one row of said two dimensional array of electrochemical cellscomprises charged electrochemical cells to be utilized as a power supplyfor said device, and wherein the remainder of said two dimensional arrayof electrochemical cells comprises information storage electrochemicalcells to be utilized for data storage detected by either measuringcharge or potential for said device.
 22. The device of claim 21 whereinsaid array of electrically conductive probes comprises an array ofatomic force microscopy tips.
 23. The device of claim 21 furthercomprising a means of determining when each of said electricallyconductive probes is in electrically conductive contact with said firstelectrode.
 24. The device according to claim 23 wherein said means ofmeasuring when each of said electrically conductive probes is inelectrically conductive contact with said first electrode comprises alaser beam.
 25. The device of claim 21 wherein said second electrode ison the entire bottom surface of said substrate.
 26. The device of claim21 wherein said second electrodes is a plurality of second electrodesunderneath each of said electrochemical cells respectively.
 27. Thedevice of claim 26 wherein each of said second electrodes is inelectrically conductive contact with each other.
 28. The device of claim21 wherein said electrochemical cells have differing open circuitpotentials.
 29. The device of claim 21 wherein said first electrodecomprises a plurality of electrodes having differing materials.
 30. Thedevice of claim 29 wherein said plurality of first electrodes havingdiffering materials allow permanent, non-erasable data to be stored anddetected by measuring the differing potentials of the first electrodesand/or binary information to be recorded and erased by charging anddischarging the electrochemical cells.
 31. The device of claim 21further comprising electrical circuits forming a grid pattern acrosssaid array of electrically conductive probes to connect each of saidelectrically conductive probes to electronic instrumentation capable ofapplying said charge, reading said charge, or discharging each of saidelectrochemical cells at different rates and/or measuring potential ofeach of said electrochemical cells.